1. Field of the Invention
This invention relates generally to a system and method for determining a thread profile, such as the angular position of the lead thread, standard thread characteristics, and thread defects in a threaded bored, and, more particularly, to a system and method for determining the starting location of the lead thread in a threaded bore, for example, in a cylinder head for a vehicle so that an end of a spark plug threaded into the bore has a desired rotational angle in the cylinder, where the system is a vision-based system.
2. Discussion of the Related Art
As a critical application in the art, a cylinder head for a vehicle is typically an aluminum structure that includes threaded bores that accept spark plugs in a threaded engagement so that an end of the spark plug is properly oriented in the cylinders of the vehicle engine. A vehicle design considers many things including engine performance. One area that provides improved engine performance for a certain engine design includes providing a proper rotational orientation of the spark plug within the cylinder that will provide the best fuel economy. In order to provide the proper rotational orientation of a spark plug, the threaded bore that the spark plug is threaded into needs to be tightly controlled so that when the spark plug is threaded into the bore the rotational orientation of the spark plug is at the desired location. In order to accomplish this goal, it is necessary to know the location of the lead thread in the threaded bore so that when the spark plug is threaded into the bored, it stops at the proper location.
There is presently no method and/or apparatus for a standard manufacturing procedure to identify and determine the location of the start of the lead thread in a threaded hole. A manual visual inspection process can be used including using a rigid or flexible borescope. Manual borescopes are very slow, are subject to human visual performance and can only be used for periodic checks to verify the start thread when parts are found defective after assembly.